Transmit power amplifiers can generate interference in various frequency bands, both proximal and distant to the signal frequency.
Interference in the receive frequency band generated by a transmit power amplifier is commonly reduced by means of filtering. Usually a combination of band-pass and band-stop filters are used to reject interference in the receive frequency band or bands. Depending on the frequency separation between the receive and transmit frequency bands, the filters required for adequate interference rejection can be large in size and weight, and of high cost. They also introduce signal power loss after the transmit power amplifier. In some applications, because of the small separation of receive and transmit frequency bands, a filter approach is impractical.
Feed-forward linearization has been used to correct receive frequency band interference. However, feed-forward system solutions tend to be quite complex and also introduce loss after the transmit power amplifier.